Aerating apparatus



Dec. 4, 1945. L H L UE 2,390,111

AERATING APPARATUS Filed Aug. 7. 1943 2 Sheets-She et l Fig.2

LELAND H. LOGUE INVENTOR.

ATTORNEY Dec. 4, 1945.

1.; 1-1. LOGUE AF-RATING APPARATUS" Filed Aug. 7. 1943 2 Sheets-Sheet 2Fig. 4 LELAND H. LOGUE INVENT OR.

ATTORNEY Patented Dec. 4, 1945 UNITED STATES" PATENT OFFICE seas-rusemans'rus Leland H. Logue, Denver, Colo alaignor to Mining Process andPatent Company, Denver, Colo., a corporation of Delaware ApplicationAugust 7, 1943, Serial No. 497,749

Claims. (01. 261-43) proportion to the amount of air delivered and,

also has required high velocity discharge causing an undue amount ofagitation. The combined efiect of high pressure gas and high velocitydischarge causes la'rge bubble formation as the gas passes from theimpeller, and the coalescence of these large bubbles impedes theflotation action.

It is an object of the present invention to provide a simple, economicaland efllcient apparatus for delivering an aerating gas within a-liquidbody at relatively low velocity and in relatively high volume,

Another object of the invention is to provide an aerating apparatus inwhich an aerating gas is distributed in volume throughout a liquid bodyin finely dispersed condition.

A further object of the invention is to provide simple, durable andeiilcient aerating apparatus which is capable of delivering asupercharged gas into a body of liquid to be aerated.

Other objects reside in novel details of construction and treatments,all of which will appear in the course of the following description..

In its broadest concept the present invention resides in the discoverythat a supercharged gas can be delivered into a zone of centrifugalinfinance within a fluid body exposed to the atmosphere at pressuresless than the hydrostatic pressure of said body and thereafterdischarged by the centrifugal influence to permeate the liquid in flnelydispersed condition.

By so introducing the gas, the eifect a machine of given capacity is todeliver a gas of greater density within a space of constant volume provided for reception of the gas and in this way attain the effect ofhaving provided an increased volume of gas to the machine.

The method may be performed in a variety of apparatus embodying featuresof the present invention -in which the aerating process is performed. Inthe drawings, in the several views of which-like parts have beendesignated similarly:

Figure l is a front elevation of a niulti-cell ma-- chine embodyingfeatures of the present invention, partially broken away to showinterior parts insection;

Figure 2 is an and elevation of the machine or Figure 1, partiallybroken away to show details of the feed delivery seal; 4

Figure 3 is a vertical section through another form of multi-cellmachine embodying features of the present invention;

Figure 4 we section taken along the line 4-4, Figure 3; and

Figure 5 is a fragmentary section, drawn to an enlarged scale, and takenalong the line 5-5.

. Figure 4. I

An impeller 0 carried on a shaft 9 is disposed for rotation adiacent thebottom of each of the cells A and B. The shaft is journalled in bearingslo and II supported on superstructure l2 above the tank and sheaves IIat the upper end of shaft 9 are provided for driving connection with asuitable prime mover, here indicated as an electrio motor I.

standard treatments, such as froth flotation, conditioning pulps forflotation, and similar treatments where a considerable degree ofaeration is required.

Pulp is fed to each cell in a series through a feed 00:: or compartmentis located between adjoining walls lo and la, and in all compartmentsii) except the first in a series a weir overflow l6 controlled by asuitable gate or other regulating means I] determines Elle volume ofpulp 0.1501131'8- mg from a preceding cell to provide the feed to asucceeding cell.

Preferably each of the walls Ia will be apertured at its upper end asindicated at it in Figure l to recirculate middlings particlescollecting in the upper portion or the pulp body back through the feedcompartment It. A gate or other regulating means I! is provided tocontrol this recirculation.

The impeller 8 preferably is covered ,by a hood The accompanyingdrawings illustrate typical as 2| having peripheral vanes 2| and ahollow column 22 extends from a top opening in hood 2! in encasingrelation to shaft 8 and at its top is sealed from the atmosphere in amanner hereinafter to be described. A feed delivery conduit 23 conductspulp from compartment I! to a point of discharge in column 22.

In the practice-of the present invention it is necessary to seal the gasdelivered to the impeller from escape to the atmosphere other thanthrough release into the pulp body. For this reason provision is made toestablish a liquid head above the intake to conduit 23 at all times anddespite feed fluctuations and regulations of weir overflow I.

As will be understood by reference to Figure 2, an arched casting 24 ismounted on wall la in overhanging relation to the intake opening ofconduit 23 and 13115 the space between wall Ia and weir 16. As aconsequence of this arrangement, pulp entering compartment I! has todescend across the sides of arch 24 to the underside of same before itcan enter conduit 23.

This deviation in flow causes the pulp to normally stand in compartmentl at the approximate position indicated by the dotted line :2: in Figurel. The height of the pulp level above arch 24 is determined by thefactors of rate of pulp feed, volume of gas delivered to the impellerand the pressure at the impeller intake. As the pressure increases, thepulp level rises until the pressure is balanced by the hydrostaticpressure in compartment l5.

Gas is supplied to the machine through a header 25 and a conduit 28connecting with the hollow column 22. Preferably, the gas supply of theheader will be at constant pressure through use of a centrifugal blower(not shown) and under such circumstances individual valve regulation ofconduits 26 will be unnecessary, although when desired a valve 21 may beprovided to control the ga introduction.

The impellers of such machines are designed to operate at a capacityconsiderably in excess of any normal volume of feed that is supplied tothem and consequently exert a suction influence on matter descendingthrough column l5. Advantage is taken of this in the present inventionto deliver the supercharged gas into the impellet at a relatively highdensity. 4

The action may be likened to the supercharging of an internal combustionengine. The cylinder is of constant volume and its piston has only afixed displacement. Obviously, the volume of the gas charge isabsolutely limited by these factors, and no increase beyond such limitscan be effected.' However, by supercharging, the density of the gasis-increased to a considerable extent, and the eflect of this on thefuel-gas intermixture is equivalent to an increase in volume of 'it ispossible, even at the relatively low pressures emp oyed, to deliver agas having a density of about two atmospheres. Consequently, theintermixing at the impeller intake and within the impeller 8 serves toentrain and entrap the gas in the high velocity pulp streams moving inand through the impeller.

The subsequent discharge of these intermixtures into the pulp body incells A and B releases the finely-dispersed gas which rises through theliquid to the surface. Due to the fact that the gas is introduced intoth impeller at a pressure less than the hydrostatic pressure above theimneller there is no high velocity discharge of gas across the impellerand consequently turbulence in ,the aerating zone is greatly reduced.

The machine illustrated in Figures 1 and 2 has a sand relief hole 30located in the lower portion of weir partition l6, and heavy solids notelevated across the weir are moved through this opening from a precedingcell to a succeeding cell in the series.

In the multi-celi operation illustrated in Figures 1 and 2, conditionedpulp is delivered from a a source (not shown) into the feed compartmentl5 of cell A and passes under an arch member 24 to enter feed deliveryconduit 23. A desired pulp level is maintained in cell A by regulationof its overflow gate ll.

Air from header 2! is delivered through line 28 into column 22 at aconstant pressure which is less than the hydrostatic pressure above theimpeller 8, and of greater density than normal atmospheric density. Thisair stream initially mixes with pulp flowing through conduit 23 at theintake side of the impeller and substantial quantities are entrained, asa result.

Thereafter the pulp and gas streams are drawn into the impeller by itssuction influence and the centrifugal action completes the entrainmentand entrapment of gas in the circulating pulp. Because of the lowpressure gas employed, there is no forceful gas discharge from theimpeller except as it is carried into the pulp body by the associatedpulp streams in the impeller.

Upon release in the pulp body beyond the zone of influence of theimpeller the gas rises as small bubbles without appreciable coalescenceuntil it reaches the surface. The action of the collector reagents inthe aerated pulp causes the mineral to be recovered to respond to thisaerating influ ence and rise to the surface and collect in a froth,which is pushed across an overflow lip 29 by rotary skimmers or paddles30.

The froth so collected is conducted by a launder (not shown) to asuitable collection or retreatment stage. Where a rougher-cleaneroperation is employed, cell A may be a rougher cell in which event thecollected froth would be recirculated through a subsequent cleaner cell,or cell A may be a cleaner cell in which collected froth from subsequentcells will be returned for retreatment. Where the latter practice isfollowed a normally closed opening in the front wall 28 of the machlneis utilized as the connection for the returned concentrate, andpreferably a conduit will conduct such concentrate from the opening 32to the intake side of impeller 8. e

The pulp residue of this initial separation is passed across weir II orthrough sand relief hole II into the feed compartment of a second cell13 which may be the end cell of a series, as illustrated, or anintermediate cell of such series, The action in cell 8 is the same asthat described with reference to cell A except that the gate II is setto permit some recirculation of middllngs from cell 8 back throughcompartment I! and it is this middlings product together with the pulpfrom cell A which constitutes the pulp feed through conduit 22 of cellB.

After the pulp is aerated in cell 8 in the manner hereinbeforedescribed, the mineral collected as a froth is skimmed across overflowlip 29, while the non-floated solid discharge across the overflow weiror through the sands relief hole I. and finally discharge through theopening 33.

If this opening is the final taillngs discharge of the machine asuitable conduit (not shown) is connected into the opening for removalof the tailings. However, if the cell B is an intermediate cell in aSeries, then the opening it acts as a seat for the feed delivery conduit23 in the next cell in the series.

The form of the invention shown in Figures 3, 4 and 5 involves the sametype of aerating action. A two cell machine has been illustrated whichmay be used as a conditioner unit or as a flotation machine. The tank 36of this form also i divided by double wall partitions 31a and 311) intotwo cells C and D.

An impeller 38 is mounted on a. shaft 39 for rotation in each cell andthe shaft is journaled in bearings 40 and ii supportedon superstructured3. Sheaves 43 on the shafts 39 are driven by a prime mover such as amotor M.

The space between adjoining partitions 31b and 31a serves as a feedcompartment 45 which may be either the original feed box of the machineas in cell C, or arr-intermediate compartment as in cell D. In theintermediate and final compartments of the machine, the compartment 45is divided by a weir 46, the overflow level of which is varied by anadjustable gate i1.

Preferably the impeller 38 is covered by a hood 56 having downwardlyprojecting blades 5| encompassing the periphery of the impeller. Ahollow column 52 extends upwardly from the hood in enclosing relation toshaft 39, and a feed deliv ery conduit 53 conducts pulp from the feedcompartment 45 into the lower end of column 52 immediately above theimpeller.

Supercharged gas is supplied to the machine by a header (not shown) andsupply conduits 56 deliver the'gas from the header into hollow column52. The gas, after delivery into column 52, is sealed from theatmosphere until it passes into the impeller and is subsequentlydischarged by the centrifugal influence of the impeller.

This involves sealing the intake end of feed delivery conduit 53 and theupper end of column 52. A gate 5! is mounted in guides 82 'for slidingmovement. An extension arm 63 on the gate is pivotally connected with alever 64 pivoted to superstructure 42 as indicated at 65 and having itsouter end fitted in a slotted guide permitting precision adjustment ofthe gate 6i relative to the intake of conduit 53.

The sealing arrangement for column 52 has been illustrated on anenlarged scale in Figure 5. The bearing housing M terminates in a skirtportion 61 which is inserted in and has a friction lit with the end ofcolumn 52 and suitable packing 38 is fitted between skirt 61 and column52 to prevent any escape therethrough.

The bearing housing has a bore for reception of the shaft 39 and isrecessed in it upper portion adjacent the bore as indicated bythereference numeral 69. In this recess, two cup washers 10a and 10b ofleather or other suitable flexible material are held in clos contactwith shaft 39 by springs H. The upper of said washer 10a preventsdescent of grease along the'shaft, while washer 10b prevents upwardescape of the supercharged gas along shaft 3e.

When the machine of Figures 3, 4 and 5 is used as a conditioner unit,pulp'is fed into feed compartment 5 of cell C and the restriction gateBI is adjusted relative to the intake end of feed delivery conduit 53 toinitially determine the maximum volume of pulp that can be delivered tosaid conduit.

The weir overflow gate 41 also is set :for optimum conditions and thecell is filled with pulp to the overflow level determined by this weirreguiation. Reagent, such as a flotation collector reagent, or adepressant, which may beeitner wet or dry, is fed into compartment 45,or directly into cell C.

Supercharged air is supplied to the treatment through line 65, passinginto column 52 where it is effectively sealed from the atmosphere by cupwasher 10b in bearing, 4| and by a liquid head above the intake tocolumn 53 provided by the setting of restriction gate 6|. air, pulp andreagent delivered onto impeller 38 through the lower end of column 52 isinitially mixed by the cascading action of the separate streams, and isfurther mixed within the impeller by the centrifugal action causingsubstantially the entire volume of gas to be entrained in thecirculating pulp streams.

The intermixture, upon discharge into the pulp body in cell C, by thecentrifugalaction of the impeller distributes throughout the cell andthe released gas rises through the liquid as minute bubbles effecting agentle but thorough aeration of the pulp.

The'reag'ent is caused to go into solution or becomes highly emulsifiedby the initial mixing and subsequent aeration. As a result, the mineralparticles are surface coated. The conditioned mineral may be collectedas a froth and separately removed for treatment at a subsequent stage,while the pulp residue is passed over weir 45 and through sands reliefhole 60 to constitute the feed to compartment 45 of cell D,

In the latter cell, the aforesaid action is repeated with the balance ofthe pulp conditioned therein and discharged through a tailings outlet 13for treatment at a subsequent stage of the operation. While theaforesaid treatment is effective with many reagents, some materials willrequire a greater degree of mixing than is afforded by the aforesaidaction.

In such instances, the cells C and D are provided with the recirculationoverflows shown at l8, IS in Figure 1 and the aerated matter collectingas froth is overfiowed into compartment 45 and in that way subjected torepetitions of the mixing and aerating actions. When so operated, nofroth is overfiowed from the machine and the discharge through outlet I3is the final ll of Figure 3 are duplicates. Therefore, the detail viewFigure 5 applies equally to the structure of Figures 1 and 3, althoughit has been drawn with special reference to the structure of Figure 3.

In all of these operations, air is added under a pressure less than thatcreated by the hydrostatic head of pulp above the impeller, and the airdelivered to the impeller intake is of a density in excess of theprevailingatmosphexic density at the location of the machine- Inutilizing a hollow column as the means for delivering the superchargedgas to the impeller, it is necessary to seal the upper end of the columnso that the gas does not escape to the atmosphere along the shaft. Andwhen the pulp is fedinto The mixture of this column to supply theimpeller, it is necesgary that no escape or gas through the incomingfeed shall be permitted.

Two means- 01 sealing the feed intake have been shown. In the form shownin Figure 1 no regulation is provided but in the form shown in Figure 3,selective regulation the head above the feed intake opening can beobtained.

Since the atmospheric pressure is uniform at any given stage in theoperation, a uniform air supply is most desirable. For this reason,individual valve regulation of the air supplied to individual cells isnot recommended, as involving undue operator attention. However, underspecial circumstances such regulation may be advantageous, and thearrangement has been illustrated in Figure l for that purpose.

It will be obvious from the foregoing description, that the introductionof supercharged gas to aerating apparatus has highly beneflcial effects,and as typifled by the arrangements illustrated in the drawings, may beapplied to a'variety of apparatus in which such treatments areperformed. Changes and modifications may be availed of within the spiritand scope of the in-' vention as deflned in the hereunto appendedclaims.

What I claim and desire to secure by Letters Patent is:

1. Aerating apparatuscomprising a tank for fluent matter open to theatmosphere, a rotary impeller in the lower portion of the tank, a covermember overhanging .the impeller and having a central opening, a hollowcolumn extending upwardly from the opening and sealing it from theatmosphere, a source of gas under constant pressure, means fordelivering gas from the source into said column at a pressure less thanthe hydrostatic pressure of said body at the impeller, a feed deliveryconduit having a discharge outlet in the hollow column above the centralopening, and means for at least partially restricting the conduit tomaintain a head oi liquid over its intake opening, whereby feeddischarged into said column forms a vortex in its passage into thecentral opening under the pumping action of the impeller and entrainsthe low-pressure gasin said movement.

2. Aerating apparatus comprising a tank for fluent matter open to theatmosphere, arotary impeller in the lower portion of the tank, a covermember overhanging the impeller and having a central openin a hollowcolumn extending up-.

. discharged into said column forms 'a vortex in its passage into thecentral opening under the' pumping action of the impeller and entrainsthe low-pressure gas in said movement.

3. Froth flotation apparatus comprising a cell tor the pulp having oneof its sides providing a iroth overflow, a pulp-delivery compartment atone end of the cell adjacent the overflow, an

adjustable weir overflow at the opposite end of said cell controllingthe discharge of pulp therefrom, a rotary impeller in the cell, a covermember overhanging the impeller and having a cen- 5 tral opening, ahollow column extending upwardly from the opening and sealing it fromthe atmosphere, 9. source of gas under constant pressure, means fordelivering gas from the source into said column at a pressure less thanthe hydrostatic pressure of said body at the impeller, a feed conduitarranged with its intake in the pulp-delivery conduit having a dischargeoutlet in the hollow column above the central opening, and means for atleast partially restricting the conduit to maintain a head of liquidover its intake opening, whereby pulp discharged into said column formsa vertex in its passage into the central opening under the pumpingacition oi the impeller and entrains the low-pressure gas in saidmovement.

4. Froth flotation apparatus comprising a cell for the pulp having oneof its sides providing a.

froth overflow, a pulp-delivery compartment at one end of the celladjacent the overflow, an adjustable weir overflow at the opposite endoi said cell controlling the discharge of pulp therefrom, a rotaryimpeller in the cell, a cover member overhangin the impeller and havinga central opening, a hollow column extending upwardly' from the openingand sealing it from the atmosphere, a source of gas under constantpressure, means for delivering gas from the source into said column at apressure less than the hydrostatic pressure of said body at theimpeller, and a feed conduit arranged with its intake in thepulp-delivery conduit and having a discharge outlet in the hollow columnabove the central opening, and flow-control means at least partiallyrestricting the conduit to maintain a .40 head of liquid over its intakeopening, whereby pulp discharged into said column forms a vortex in itspassage into the central opening under the pumping action of theimpeller and entrains the low-pressure gas in said movement.

5. Froth flotation apparatus comprising a cell for the pulp having oneof its sides providing a froth overflow, a pulp-delivery compartment atone end of the cell adjacent the overflow, an adjustable weir overflowat-the opposite end of said cell controllingthe discharge of pulptherefrom, a rotary impeller in the cell, a cover member overhanging theimpeller and having a central opening, a hollow column extending up-"wardly from the opening and sealing it from the atmosphere, a source ofgas under constant pressure, means for delivering gas from the sourceinto said column at a pressure less than the hydrostatic pressure ofsaid body at the impeller, a feed conduit arranged with its intake inthe pulp-delivery conduit and having a discharge outlet in the hollowcolumn above the central opening, an adjustable gate member forpartially restricting the intake of the conduit sealing it from theatmosphere, whereby pulp discharged into said column forms a vortex inits passage into the opening under the pumping action of the impellerand entrains the low-pressure gas in said movement, and control meansfor said ate mounted at-the top oi'said cell.

LELAND H. LOGUE.

